Diver propulsion vehicles (DPVs) generally comprise a battery, a motor, a driveshaft, a driveshaft seal or other technologies to prevent water from leaking up the driveshaft into the motor, a propeller, a propeller guard, a handle, motor controls, and a hull in which or to which the other components are mounted.
Conventional DPVs have efficiency issues of propeller-driven craft. For example, a motor-propeller efficiency curve for watercraft is roughly shaped like an inverted parabola, with the high point at a target speed. When the watercraft deviates from the target speed and goes “too fast” or “too slow”, efficiency drops off in a non-linear manner.
DPVs are used in contexts that may include low visibility, currents, expected and unexpected obstructions, and the like, which creates an imperative toward safety in design of DPVs. In addition, foreign objects such as fingers, dive equipment, rocks, flotsam and jetsam, fish and the like may intersect with the propeller of a DPV in an unpredictable and hazardous manner. For example, fingers may be severely injured by a propeller, air tubes may be cut, and/or the function of the propeller and operation of the DPV may be impaired by intersection of a foreign object with the propeller. A propeller guard may be added to or increased in size around the propeller to make the DPV safer; however the larger the propeller guard is and the more safely the propeller is encased, the less efficient the DPV becomes. Similarly, an impeller may be used instead of a propeller, but impellers are less efficient than propellers.
More efficient DPVs have larger propellers with less propeller shielding, which makes such DPVs less safe.
Conventional propeller-driven DPVs also may produce noise, due to operation of the propeller and motor. Such noise may change the behavior of fish, may be unpleasant to the operator of the DPV, may be heard, and may otherwise be undesirable. Advanced propeller and motor design may reduce such noise, though at significant expense.